using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using EasyNetQ;
using MalwareMultiScan.Backends.Interfaces;
using MalwareMultiScan.Backends.Messages;
using MalwareMultiScan.Scanner.Services.Interfaces;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace MalwareMultiScan.Scanner.Services.Implementations
{
    /// <inheritdoc />
    public class ScanHostedService : IScanHostedService
    {
        private readonly IScanBackend _backend;
        private readonly IBus _bus;
        private readonly IConfiguration _configuration;
        private readonly ILogger<ScanHostedService> _logger;

        /// <summary>
        /// Initialise scan hosted service.
        /// </summary>
        /// <param name="logger">Logger.</param>
        /// <param name="backend">Scan backend.</param>
        /// <param name="bus">EasyNetQ bus.</param>
        /// <param name="configuration">Configuration.</param>
        public ScanHostedService(
            ILogger<ScanHostedService> logger,
            IScanBackend backend, IBus bus,
            IConfiguration configuration)
        {
            _logger = logger;
            _bus = bus;
            _configuration = configuration;
            _backend = backend;
        }

        /// <inheritdoc />
        public Task StartAsync(CancellationToken cancellationToken)
        {
            _bus.Receive<ScanRequestMessage>(_backend.Id, Scan);

            _logger.LogInformation(
                $"Started scan hosting service for the backend {_backend.Id}");

            return Task.CompletedTask;
        }

        /// <inheritdoc />
        public Task StopAsync(CancellationToken cancellationToken)
        {
            _bus.Dispose();

            _logger.LogInformation(
                $"Stopped scan hosting service for the backend {_backend.Id}");

            return Task.CompletedTask;
        }

        private async Task Scan(ScanRequestMessage message)
        {
            _logger.LogInformation(
                $"Starting scan of {message.Uri} via backend {_backend.Id} from {message.Id}");

            var cancellationTokenSource = new CancellationTokenSource(
                TimeSpan.FromSeconds(_configuration.GetValue<int>("MaxScanningTime")));

            var result = new ScanResultMessage
            {
                Id = message.Id,
                Backend = _backend.Id
            };

            var stopwatch = new Stopwatch();

            stopwatch.Start();

            try
            {
                result.Threats = await _backend.ScanAsync(
                    message.Uri, cancellationTokenSource.Token);

                result.Succeeded = true;

                _logger.LogInformation(
                    $"Backend {_backend.Id} completed a scan of {message.Id} " +
                    $"with result '{string.Join(", ", result.Threats)}'");
            }
            catch (Exception exception)
            {
                result.Succeeded = false;

                _logger.LogError(
                    exception, "Scanning failed with exception");
            }
            finally
            {
                stopwatch.Stop();
            }

            result.Duration = stopwatch.ElapsedMilliseconds / 1000;

            _logger.LogInformation(
                $"Sending scan results with status {result.Succeeded}");

            await _bus.SendAsync(
                _configuration.GetValue<string>("ResultsSubscriptionId"), result);
        }
    }
}